Failure of dietary vitamin C supplementation to prevent seasonal infertility in pigs

Half the sows and boars on each of 5 commercial farms that had histories of seasonal infertility were given 4 g vitamin C daily. The other half was unsupplemented. Of 423 sows which were allocated to the experiment during the summer-early autumn of 1978-79, 392 were available for mating during the course of the study. Although the percentage of sows mating successfully was greater with vitamin C (68.0 vs. 61.2%), this difference was non-significant (P <0.05). Vitamin C had no effect on the weaning-to-conception interval of sows nor on the number of piglets born, born alive, stillborn and weaned per litter, pre-weaning mortality or litter and piglet weaning weight. There was no relationship between weekly average maximum temperature and the weekly percentage of successful matings. Although the results demonstrated that fertility was poor during the summer-early autumn, a large daily dose of vitamin C was ineffective in countering the seasonal infertility.